Updated on January 11, 2025

Function model

Note! Due to specifics of function modeling for devices and for processes, there is a slight difference between the definitions of the function model.

Function model of the device is a model of an engineering system that identifies and describes functions performed by the components of the system and its supersystem, their usefulness and performance level, and costs. 

Function model of the process is a model of an engineering system that identifies and describes functions performed within the components of the system, their usefulness and performance level, and costs. 

Overview

Function model is created during the last stage of function analysis referred to as function modeling. Along with the list of function disadvantages, it represents the final outcome of the entire analysis.

The model is the input for trimming as it provides the information about what useful functions of trimmed components should be transferred and what new carriers may be used.

Presentation

Both for the devices and for processes, the function model can be presented in two ways – either as a table or as a graph.

It the project involvs many components, the table is usually employed, since the graph could be too complicated and therefore unreadable. The graph form is usually used for systems with a small number of components.

Function model as a table

For the device, the table usually contains a list of components, their functions, categories of functions (useful or harmful), the level of performance of useful functions (normal, excessive or insufficient), and a ranking of functions (basic, additional, auxiliary), which is the basis for calculating the functionality index of the components.

If it is necessary to calculate the functionality index, it is being included in the tabular function model. In this case the model not only contains a list of components, their functions, categories of functions, the level of performance of useful functions, but also the ranking of functions (basic, additional, auxiliary), as well as the functionality index of functions

In some cases, the table can be extended with additional parameters for categorizing components and functions if this helps in classifying components, e.g. the costs of components and their values. 

The picture below presents a schematic for creating a tabular function model of a hypothetical device:

The following picture presents a schematic for creating a tabular function model of a hypothetical process:

Function model as a graph

While the tables for function models of devices and processes are quite similar, their presentation in the form of graphs differs significantly.

Graph for a device

To visualize the function model of the device, it is recommended that the shape and color coding for components implemented in component model be used. Additionally, shape and color coding for functions should be determined. Usually, it is as follows:

Using the proposed symbols, the example function model presented in the table in the Function model as a table section can be graphically represented the following way:

When creating the graph, it is important to maintain the correct direction of the arrows representing the functions, so that they clearly indicate which component is the carrier, and which is the object of the function.

Graph for a process

The function model of a process in the form of a graph is highly useful when it is necessary to reflect the relationships between operations – for instance, whether they are performed in parallel or sequentially. Below, we present the simplest graphical process model. It includes only functions and their categories. This information can be supplemented with additional data, such as the level of performance, rank, or the total score of the entire operation.

The graph represents an example of the process model described in the table above. To maintain the schematic clarity of the function graph, we used the format carrier (action) object. In place of (action), a verb describing the specific function should be inserted, e.g., carrier A moves object Z, carrier B holds object X, etc.

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